IrO2 deposited on RuO2 as core-shell structured RuO2@IrO2 for oxygen evolution reaction in electrochemical water electrolyzer

The ever-rising energy demand and environmental concerns require the application of electrochemical water splitting to produce hydrogen as a substitute energy to fossil fuel. Proton exchange membrane water electrolyzers split water into oxygen and hydrogen at the anode and cathode, respectively. Anode catalysts necessitate extensive study, because significant overpotential is required to accelerate the 4-e sluggish oxygen evolution reaction in acidic media. RuO2@IrO2 was synthesized in this work, which aims to achieve high activity and stability. In doing so, RuO2·xH2O was first prepared using the Adams method, followed by the subsequent precipitation of Ir(OH)3 on its surface via the hydrolysis of iridium precursor in a mix of NH3·H2O in ethanol. Upon heat treatment, RuO2@IrO2 with an appropriate Ru/Ir molar ratio was obtained and applied for oxygen evolution reaction. Electrochemical evaluation results show that the optimized RuO2@IrO2-20 performed the best in terms of enhanced mass activity (1.62 A mg−1oxide @1.6 V) and lower overpotential (275 mV@10 mA cm−2) compared with single RuO2 and IrO2 catalysts. In addition, both chronopotentiometry and chronoamperometry test results show that the stability of RuO2@IrO2-20 is highly competitive. The intimate contact between RuO2 and IrO2 combines both the most active RuO2 and stable IrO2 as an integrated catalyst.